The overall objective of this proposed research is to investigate by electron microscopic and cytochemical techniques the regeneration of human epidermis in healing experimental wounds. The research will comprise a continuation of on-going collaborative studies with Dr. Russell Ross on skin wound repair in normal adult man, and, using the frame of reference established by our earlier wound studies, a new analysis of the repair of experimental wounds in patients who have been maintained on long-term corticosteroid therapy. These objectives are consonant with my longer range research objectives of investigation of the submicroscopic cytological characteristics of differentiation in human epidermis. I anticipate that these long-range objectives may lead to a greater understanding of pathogenesis and therapy in those common skin diseases (chronic dermatitis, psoriasis, ichthyosis) in which kinetic, often heritable, abnormalities of differentiation appear to be prominent mechanisms of pathogenesis.